Resistive effects in solar cells reduce the efficiency of the solar cell by dissipating power in the resistances. The most common parasitic resistances are series resistance and shunt resistance. The inclusion of the series and shunt resistance on the solar cell model is shown in the figure below.
In most cases and for typical values of shunt and series resistance, the key impact of parasitic resistance is to reduce the fill factor. Both the magnitude and impact of series and shunt resistance depend on the geometry of the solar cell, at the operating point of the solar cell. Since the value of resistance will depend on the area of the solar cell, when comparing the series resistance of solar cells which may have different areas, a common unit for resistance is in Ωcm2. This area-normalized resistance results from replacing current with current density in Ohm's law as shown below:
The effects of series and shunt resistances are described in the following pages.